The present invention relates to compositions suitable for golf ball constructions and to golf balls which employ those compositions.
Modern golf balls typically employ ionomeric resins as cover materials. Ionomeric resins, as a result of their toughness, durability, and wide range of hardness values, have become materials of choice for golf ball covers over traditional rubbers. Ionomeric resins generally comprise an xcex1-olefin and an xcex1, xcex2 ethylenically unsaturated mono- or dicarboxylic acid neutralized with metal ions to the extent desired. Olefins which have been employed to prepare ionomeric resins include ethylene, propylene, butene-l and the like. Unsaturated carboxylic acids which have been employed to prepare ionomeric resins include acrylic, methacrylic, ethacrylic, o-chloroacrylic, crotonic, maleic, fumaric, itaconic and the like. Ionomeric resins include copolymers of ethylene with acrylic acid such as those sold by Exxon Corporation under the trademark xe2x80x9cIOTEKxe2x80x9d, as well as copolymers of ethylene with methacrylic acid such as those sold by E. I. DuPont Nemours and Company under the trademark xe2x80x9cSURLYNxe2x80x9d. In some instances, a softening comonomer such as an acrylate ester has been included such that the ionomeric copolymer is an ionomeric terpolymer. Although various compositions have been employed to provide golf balls of varying playability characteristics, a need continues for compositions and covers which can be employed to provide golf balls which exhibit good playability and durability.
There are no commercially available golf balls which are generally known to contain nylon. Nylon alone would be too brittle for use in a golf ball cover. When efforts have been made in other fields to blend nylon with softer materials some degree of incompatibility often has resulted, rendering the blends susceptible to cracking and premature failure. U.S. Pat. No. 4,690,981, the contents of which are incorporated herein by reference, shows soft terpolymer ionomers of ethylene/unsaturated carboxylic acid/softening comonomer which are useful in injection-molded items such as ski boots, ice skate shells, as coatings for fabrics, and as a replacement for balata in golf balls. The unsaturated carboxylic acid may be, for example, acrylic acid and methacrylic acid. The softening comonomer is, for example, an alkyl acrylate such as n-butyl acrylate. The ""981 patent briefly mentions that the ionomers can be blended with other materials such as nylon, polypropylene, propylene-ethylene copolymers, linear polyethylene, and ethylenelunsaturated carboxylic acid copolymers. However, there is no indication that blends can be used for golf balls.
In view of known strength and durability properties of nylon, it would be desirable to somehow utilize nylon in the construction of a golf ball. Specifically, it would be desirable to identify particular types of nylon materials that might be uniquely adapted to serve as materials for golf ball construction. There is a particular need for improved golf ball cover materials.
An object of the invention is to provide a highly durable golf ball.
Another object of the invention is to provide a golf ball with a cover layer containing reduced quantities of ionomer.
A further object of the invention is to provide a golf ball having a high coefficient of restitution.
Another object of the invention is to provide a durable golf ball with a low spin rate.
Yet another object of the invention is to provide a golf ball having a hard cover layer which is resistant to cracking.
Another object of the invention is to provide a method of making a golf ball with a cover layer of the type described above.
Other objects of the invention will be in part obvious and in part pointed out more in detail hereinafter.
A preferred embodiment is a golf ball having a core and a cover disposed about said core. The cover includes polyphthalamide.
Another preferred embodiment is a golf ball having a cover and a core centrally disposed within said cover. The cover includes a combination of a first component and a second component. The first component comprises a polyamide including a polyphthalamide formed from reacting an agent including at least one of phthalic acid, isophthalic acid, and terephthalic acid. The second component comprises an ionomer.
Yet another preferred embodiment is a method of making a golf ball comprising the steps of: (1) obtaining a golf ball core; and (2) forming a cover layer over the core, said cover layer having a resin composition comprising a combination of a polyphthalamide component and an ionomeric component, the amount of said polyphthalamide component being at least 10 wt. % of said resin composition; and said golf ball having a coefficient of restitution of at least 0.750.
The invention comprises the several steps and the relation of one or more such steps with respect to each of the others, and the article possessing the features, properties and the relation of elements exemplified in the following detailed disclosure.